SKF
Lock Nuts Requiring a Keyway
Lock nuts requiring a keyway are the most common type, consisting of a nut (e.g., KM series) and a corresponding lock washer (MB series) with an inner tab that engages a shaft keyway and outer tabs that bend into slots on the nut’s circumference. This positive mechanical lock prevents loosening. SKF produces these in metric (KM/KML) and inch sizes, with fine-pitch threads to achieve high clamping forces. They are suitable for most industrial bearing applications, including electric motors, gearboxes, and conveyors. The simple design enables quick assembly with a hook or peg spanner. When correctly installed, they provide secure, maintenance-free retention throughout the bearing’s service life.
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Trusted by Industry Leaders
Positive Mechanical Lock
Keyed washer prevents rotation under vibration.
Wide Size Range
KM and KML series from small to large bores.
High Clamping Force
Fine-pitch threads multiply tightening torque into axial force.
Easy Visual Inspection
Bent tabs provide clear indication of proper locking.
Reusable in Maintenance
Nuts and washers can be refurbished if tabs are not fatigued.
Cost-Effective Retention
Simple, proven design for mass-market applications.
Installing KM Lock Nuts and MB Washers Correctly
Slide the MB washer onto the shaft, engaging its inner tab in the keyway. Tighten the KM nut. Align a washer outer tab with a nut slot, bend it into the slot. This secures the nut. Never reuse a washer with already-bent tabs if they are fatigued; replace with a new one to guarantee locking.
Where Keyway Lock Nuts Excel
Normal motors, pumps, and fan bearings with modest vibration levels benefit from this straightforward solution. They are standard in SKF’s bearing unit lines and are widely understood by maintenance teams, reducing training needs.